The present invention relates to an electron beam lithography method and apparatus, and more particularly to an electron beam lithography method and apparatus in which patterns periodically repeated in an LSI circuit or the like are delineated or written at high speed and with high accuracy.
An electron beam lithography method is a technique indispensable to the research and development of most advanced devices because of a feature that minute patterns can be formed with no mask. However, there is a problem that the throughput is low since the patterns are successively delineated. In order to greatly improve the throughput, JP-A-62-260322 has proposed a method in which an aperture of an electron beam lithography apparatus includes an array of unit patterns repeatedly arranged. An electron beam emitted from an electron beam source is passed through this aperture so that a substrate is irradiated with an electron beam shaped through the aperture (hereinafter referred to as a fixed shaped beam) for pattern delineation.
The present inventors have examined the above electron beam lithography method and have found out the following new problems.
In the fixed shaped beam, it is not possible to change the beam exposure intensity (or the quantity of beam radiation) within one exposure shot. An inconvenience caused by this fact appears, for example, at the periphery portion of a semiconductor memory cell array as shown in FIG. 1. For example, when a 64 Mbit cell pattern is delineated, eight wiring patterns (corresponding to a 32-bit memory portion) are included in one shot of a fixed shaped beam of 7 .mu.m square, as shown in FIG. 1A. In the outermost periphery of the memory cell array shown in FIG. 1B, the pattern density has a large change. Therefore, there is a problem that in the 7 .mu.m square, a pattern 2 on the outermost periphery has a lack of exposure due to a proximity effect and hence the accuracy in dimension is deteriorated.
Also, in the prior art, the number of minimum units or unit patterns repeatedly arranged in the aperture is not taken into consideration. However, this number of unit patterns in the aperture has an important significance in improving the throughput.
Further, the present inventors have revealed that it does not always follow that the line width of a pattern delineated on the substrate has a one-to-one correspondence to the aperture width (or the width of an opening) of the above aperture. This can be considered to be caused by an influence of the type or thickness of a resist on a substrate.